The present invention relates to a controller for an automatic repair unit (hereinafter auto-repair unit) which corrects abnormal weaving operates on a loom. More particularly, the present invention relates to a controller which is capable of prohibiting operation of an auto-repair unit when the frequency of auto-repair operations has exceeded a preselected limit.
As used herein, the term "production index" refers to a value indicative of the quantity of cloth produced by the loom. Production time, the number of weft insertions which have taken place during production, and the length of cloth produced are examples of such a production index. As used herein, the term "present production index" shall refer to a predetermined production index during which a determination is made as to whether the rate of auto-repair operations, and therefore the rate of weaving defects is acceptable. The term "production period" shall refer to the time it takes for the production index to reach the preset production index.
When an abnormal weaving operation has started on a loom, an auto-repair unit operates to arrange a situation suited for restarting the loom. One typical example of such an auto-repair unit is a faulty weft remover unit. When abnormal weft insertion has started on a loom and loom crank rotation has been stopped, the loom crank is rotated over almost one cycle in a direction opposite to the normal direction of the loom in order to open the shed of the faulty weft and release the faulty weft. Next a faulty weft remover unit operates to remove the faulty weft from the open shed.
One example of such a faulty weft remover unit is disclosed in Japanese Patent Opening No. Sho. 58-220856. The assignee of this application has proposed some examples of such a faulty weft remover unit in Japanese Patent Applications No. Sho. 59-156097 and No. 59-170757.
On receipt of a detection signal indicating an abnormal weft insertion, the faulty weft remover unit automatically operates to remove a faulty weft from its shed. Neither manual labor nor manual discrimination is involved in this removal of the faulty weft. Other types of auto-repair units operate on the same principle and in the same fashion.
Some types of abnormal weaving are likely to repeat continuously when the source of trouble is not removed. Abnormal weft insertion caused by abnormal shedding is one typical example. Repeated abnormal weaving operation tends to enlarge weaving defects despite the operation of the auto-repair unit and seriously deteriorates the cloth produced. The presence of apparent or enlarged defects on a cloth lowers its grade seriously.
At the beginning of an auto-repair operation, the auto-repair unit starts its operation on receipt of a detection signal indicative of the presence of abnormal weaving operation without regard to the source of the trouble. Such an abnormal situation may be detected by an operator when the production is under even partial manual control. In the case of fully automatic control of the production, however, such an abnormal situation cannot be detected and, as a consequence, operation of the auto-repair unit is repeated continuously until the production itself ends. Thus, weaving defects initially caused by the abnormal weaving are cumulatively enlarged to significantly degrade the cloth produced even below C-grade.